Transcription Flashcards
(20 cards)
What controls protein levels in a cell?
Rate of transcription, mRNA degradation, protein synthesis, and protein degradation.
Why study prokaryotes for transcription?
Fast replication, simple gene structure, and straightforward gene regulation.
What is an operon?
A cluster of genes transcribed together, often regulating a specific process (e.g., lac operon).
What does RNA polymerase do?
Synthesizes RNA using DNA as a template.
What is a promoter?
A DNA sequence where RNA polymerase binds to start transcription.
What is the function of a sigma factor?
Helps RNA polymerase bind to the promoter.
What is polycistronic mRNA?
A single mRNA molecule that encodes multiple proteins.
What is a transcription factor?
A protein that binds DNA to regulate transcription.
What are co-activators and co-repressors?
Co-activators stimulate transcription; co-repressors inhibit it.
What is a consensus sequence?
A common DNA sequence recognized by transcription machinery, e.g., -10 and -35 regions in prokaryotes.
What is the transcription start site (TSS)?
The first nucleotide transcribed into RNA.
What happens when a repressor binds to an operator?
It prevents RNA polymerase from initiating transcription.
How does the Lac Operon get activated?
Presence of lactose binds to the repressor, detaching it from the operator, allowing RNA polymerase access.
Why is gene regulation simpler in prokaryotes than eukaryotes?
Prokaryotes have polycistronic mRNAs and less non-coding DNA.
What is the role of cis-regulatory elements?
DNA sequences that transcription factors bind to for controlling gene expression.
Why is studying the structure of genes important?
It reveals how replication, transcription, and translation are regulated and how errors drive evolution.
Why doesn’t a high transcription rate always mean high protein levels?
Post-transcriptional regulation and protein degradation also affect protein concentration.
What is the difference between activators and repressors in transcription control?
Activators enhance RNA polymerase binding; repressors block it.
How do ligands affect transcription factors?
Binding to ligands can activate or inhibit transcription factors, changing gene expression.
Why might eukaryotic genomes be larger than prokaryotic ones?
More non-coding DNA, regulatory sequences, and complex control mechanisms.
